The subject invention relates to a compound spring-loaded archery bow and in particular to an improved compound spring-loaded archery bow with improved separate upper and lower spring tensioning assemblies and associated cam mechanisms for applying tension to the bowstring of the bow. The separate upper and lower spring tensioning assemblies are contained within the upper and lower rigid limbs of the bow so that the bow of the subject invention retains the appearance of a traditional archery bow while having the advantages of being a compound spring-loaded archery bow.
A traditional archery bow has a central riser with a handgrip and arrow rest plus upper and lower resilient limbs that extend upward and downward from the central riser and provide the archery bow with its traditional appearance. The central riser and upper and lower resilient limbs of the archery bow form a leaf spring. A bowstring is attached to the free ends of the upper and lower resilient limbs and as the bowstring is drawn back from its initial position by an archer to shoot an arrow the upper and lower resilient limbs flex to place the bowstring under tension. The farther the archer draws back the bowstring, the more the upper and lower resilient limbs of the bow are flexed to impart ever greater tension to the bowstring. When the bowstring is released to shoot the arrow, the upper and lower resilient limbs of the archery bow snap back to their original positions and thereby snap the bowstring back to its initial position to propel the arrow toward a selected target. While current traditional archery bows are frequently made of strong composite materials, the upper and lower resilient limbs of these bows sometimes fail and can cause serious injury. Traditional archery bows have other drawbacks. The frames of these traditional archery bows have a unitary construction so that these bows cannot be disassembled for compact storage, handling, and transport. These archery bows are manufactured to have a maximum drawing force that can not be changed with the maximum drawing force typically being set to be within a limited 10 pound range, e.g. within a 40 to 50 pound maximum pull range, within a 50 to 60 pound maximum pull range, within a 60 to 70 pound maximum pull range, etc. Thus, once an archer selects a traditional archery bow, the archer is restricted with that bow to a set maximum drawing force that is within the limited poundage range of that bow and must obtain another bow or bow limbs should he/she desire for whatever reason to utilize an archery bow having a maximum drawing force within a greater or lesser poundage range.
Compound archery bows such as the compound archery bows disclosed in U.S. Pat. No. 4,458,657, issued Jul. 10, 1984 and U.S. Pat. No. 6,698,413 are examples of compound bows that have been developed as an alternative to the traditional “leaf spring” archery bow discussed above. The compound archery bow of the '657 patent has a somewhat complicated structure with both a main frame and a handle grip and bowstring tensioning assembly located forward of the main frame. The bowstring tensioning assembly is formed by exposed resilient tubes for tensioning the bowstring, which are stretched and placed in tension when the bowstring of the bow is drawn. The exposed resilient tensioning tubes of the tensioning assembly are mounted on forward projecting wings of the bow's handle grip and are connected to cam members of the bow which, in turn, are connected to the bowstring. The compound archery bow of the '413 patent is another example of a compound archery bow. This compound archery bow only utilizes a single compressible coil spring bowstring tensioning unit which is threaded into and projects forward from a lower limb of the bow. This form of tensioning unit only permits the tension on the bowstring to be adjusted from the lower end of the bowstring and compromises the configuration of the bow so that the bow doesn't have the appearance of a traditional archery bow. Thus, while compound archery bows such as those just discussed are available, there has remained a need for an improved compound archery bow with independent upper and lower bowstring tensioning assemblies that permit the performance characteristics of the bow to be easily and accurately tuned for optimum performance and that enable the compound archery bow to retain the configuration of a traditional archery bow.